1. Field of the Invention
The present invention relates to a two-stage rotary compressor (hereinafter, also simply referred to as “rotary compressor”), and specifically to a compressor with improved compression efficiency of refrigerant by reducing pressure loss of a low-pressure connecting pipe for connecting a compressor housing and an accumulator.
2. Description of the Related Art
Conventionally, a two-stage rotary compressor includes a low-stage compressing section and a high-stage compressing section and a motor for driving the low-stage compressing section and the high-stage compressing section inside of a cylindrical compressor housing that is a sealed container, and includes an accumulator outside of the compressor housing.
On an outer peripheral wall of the cylindrical compressor housing, a first communication hole, a second communication hole, and a third communication hole are provided apart from one another on a straight line along the center axis direction of the housing, and one end of a low-stage suction pipe for sucking in low-pressure gas refrigerant Ps within the accumulator is connected through the second communication hole to a suction hole of the low-stage compressing section.
Further, one end of a low-stage discharge pipe for discharging low-stage discharge gas refrigerant Pm to outside of the compressor housing is connected through the first communication hole to a low-stage muffler discharge hole of the low-stage compressing section, and one end of a high-stage suction pipe for sucking in the low-stage discharge gas refrigerant Pm is connected through the third communication hole to a suction hole of the high-stage compressing section. The other end of the low-stage suction pipe and the accumulator are connected by a low-pressure connecting pipe and the other end of the low-stage discharge pipe and the other end of the high-stage suction pipe are connected by an intermediate connecting pipe.
Through the pipe connection, a gas refrigerant flows in the following manner. The low-pressure gas refrigerant Ps is sucked in from the accumulator, passes through the low-pressure connecting pipe and the low-stage suction pipe, is taken in from the suction hole of the low-stage compressing section into the low-stage compressing section, and is compressed to intermediate pressure to be the low-stage discharge gas refrigerant Pm.
The low-stage discharge gas refrigerant Pm at the intermediate pressure discharged to the low-stage discharge space passes through the low-stage discharge pipe, the intermediate connecting pipe and the high-stage suction pipe, is sucked in from the suction hole of the high-stage compressing section into the high-stage compressing section, compressed to high pressure to be high-stage discharge gas refrigerant Pd, discharged into the inner space of the compressor housing, and passes through a clearance between motors and is discharged from the discharge pipe to a freezing cycle side (e.g., see Japanese Patent Application Laid-open No. 2006-152931).
However, according to the above described conventional technology, since the first communication hole, the second communication hole, and the third communication hole are provided on the straight line along the center axis direction of the outer peripheral wall of the compressor housing, in order to avoid the interference with the circular intermediate connecting pipe that connects the low-stage discharge pipe and the high-stage suction pipe, the low-pressure connecting pipe that connects the low-stage suction pipe and the accumulator has a complex shape formed by three-dimensional bending at right angles in two parts. Accordingly, there has been a problem that the pipe line resistance becomes greater and the pressure loss of the refrigerant becomes greater, and thus the compression efficiency of the rotary compressor becomes worse.
Further, since the distances between the respective communication holes of the compressor housing are short, there has been a problem that the pressure resistance of the compressor housing becomes lower, and the welding (brazing) operation between the low-pressure connecting pipe and the low-stage suction pipe and the welding (brazing) operation between the intermediate connecting pipe and the low-stage discharge pipe as well as the high-stage suction pipe are difficult.